1. Field of the Invention
The invention relates generally to optical systems useful in industrial lighting applications and particularly to energy efficient and high performance luminaires incorporating such optical systems utilizing independent and concentrically aligned reflectors adjustable relative to each other and operating in tandem to produce a versatile range of tailored photometric distributions.
2. Description of the Prior Art
High bay luminaires have traditionally found particular use in warehouses, manufacturing facilities and increasingly in retail situations wherein ceiling heights require lighting adequate for illumination of particular areas within an overall space. Low bay luminaries of similar configuration find utility in lighting applications having differing lighting requirements. Conventional luminaires of these types typically provide uniform illumination over the distribution area of such facilities, such uniform illumination typically being less than adequate for at least certain areas in which a greater degree of light intensity is desirable, such as in an area in which an assembly line is located, as opposed to an area wherein a lesser degree of illumination is necessary such as walkways or the like where tasks requiring greater degrees of illumination are not performed. In typical warehouses, for example, luminaires are disposed between fifteen to seventy feet above floor level. In such situations, more light is desired at a working surface as opposed to upper portions of a storage rack or near ceiling levels. Even so, adequate illumination is necessary at these upper portions of storage racks and the like so that fork lift or “picking” operators can place and remove items from these racks. Typical high bay or low bay luminaires are incapable of providing adequate lighting levels at these spaced locations within the volumetric confines of a working space or the like without the use of high wattage lamping, thereby creating unnecessary illumination near ceilings in order to create adequate lighting near floor level. Such conventional luminaires typically use 400 watt lamps as well as lamping ranging up to 1000 watts in order to address these needs, the use of such lamps being extraordinarily wasteful of energy in the form of the electrical power necessary for operation of such lamping even without consideration for the additional energy required for space cooling due to the heat generated by this high wattage lamping.
The art has previously addressed certain of these failings through use of dual reflector lighting systems such as are disclosed by Thomas et al in U.S. Pat. No. 5,582,479; by Walker et al in U.S. Pat. No. 6,068,388 and by Splane, Jr. in U.S. Pat. Nos. 5,791,768; 6,273,590 and 6,464,377. In these patents, an inner reflector located within an outer reflector, such as is typically used as a sole reflector in a high bay luminaire or the like, can be displaced relative to the outer reflector and relative to lamping in order to produce a desired lighting distribution for any given luminaire in a building having a multiplicity of luminaires for illumination of the building. These luminaires function with lamping of a lower wattage to produce desired lighting distributions and illumination levels than would be expected given the performance of conventionally used high bay luminaires such as those disclosed in U.S. Pat. No. 3,401,258 to Guth and U.S. Pat. No. 4,173,037 to Henderson, Jr. et al, these and many other high bay luminaires being commonly used over at least the last fifty years. In these prior art luminaires, an opaque or transparent prismatic reflector typically having an inverted bowl shape houses an energy inefficient lamp in order to provide adequate illumination levels within a given volumetric space. Even though Henderson, Jr. et al disclose an outer reflector and an asymmetrical inner reflector, the inner reflector is mounted for rotational adjustment relative to the vertical axis of the disclosed luminaire and thus functions only to produce asymmetrical light distribution and does not permit energy efficiencies. Similarly, well known luminaires such as those disclosed by Cochran in U.S. Pat. No. 1,286,535 include dual reflectors incapable of displacement relative to each other to vary lighting distributions.
High bay luminaires are further disclosed by Jaffari et al in U.S. Pat. No. 6,478,454; by Burroughs in U.S. Pat. No. 6,494,596; by Sitzema, Jr., et al in U.S. Pat. No. 6,698,908; by Barnes et al in U.S. Pat. No. 4,839,781; by Taylor et al in U.S. Pat. No. 4,903,180; by Sales in U.S. Pat. No. 6,910,785 and by Leadford in U.S. Pat. No. 7,025,476. With the exception of Jaffari et al, these patents focus on transparent single reflector luminaires having prismatic structures which function to reflect light from lamping to illuminate a space. Jaffari et al disclose a metal primary or outer reflector capable of directing light upwardly of the luminaire. Burroughs treats a prismatic reflector on upper portions of inside surfaces in order to eliminate hot spots at nadir. Sitzema, Jr. et al provide a peened specular collar with a primary reflector to achieve a more narrow distribution in an acrylic high bay luminaire. Barnes et al disclose a commonly employed reflector/refractor used in luminaires and the like, such luminaires configured only with the reflector/refractor so disclosed being incapable of adjustment of light distribution characteristics along with an inability to provide desirable illumination levels with lamping of a lower wattage and thus greater energy efficiency than is possible in light of the disclosure provided herein. Sales and Leadford disclose single reflectors useable in high bay and similar luminaires, these reflectors being intended to utilize shaped prisms for direction of light from lamping housed within the reflectors.
Prismatic structures useable in luminaires such as high bay luminaires and the like are further described by Pearce in U.S. Pat. No. 5,416,684; by Shadwick in U.S. Pat. No. 3,800,138 and by Franck in U.S. Pat. No. 2,818,500. Franck discloses a number of basic lighting principles relating to prismatic structures formed of transparent materials such as high grade glass. Among these structures are radial scallops on interior surfaces of a reflector and configured to avoid light being incident on the valley and ridge radii of externally disposed prisms. Shadwick discloses scalloped structures that function to blur bleed-through lamp image viewed through a refractor functioning as a reflective structure. Pearce provides a fixed secondary metal reflector within an enclosing refractor in order to divert light away from a non-optical base of the refractor. Guth, previously mentioned, discloses in U.S. Pat. No. 3,401,258 faceted fluting in the form of radial scallops formed near the aperture of a metal or otherwise opaque reflector and used for glare control. Yet another prismatic reflector disclosed as a high bay luminaire is provided by Taylor et al in U.S. Pat. No. 4,903,180 with a transparent shroud for protection of the reflector from dust accumulation that degrades reflector performance.
The prior art fails to disclose optical systems particularly useful in high bay and similar luminaries as well as in luminaires capable of use in other lighting applications, which optical systems are capable of energy efficiencies and enhanced performance relative to presently available luminaires. Accordingly, a need for optical systems capable of energy efficiency and improved performance is long-felt and is addressed by the presently disclosed optical systems, said optical systems of the invention being characterized as dual reflector systems having precision optics utilizing highly specular reflective finishes particularly disposed on an inner reflector having radial waves or scallops either concave or convex, the assembly of the inner reflector and a clear point source lamp being displaceable relative to a prismatic outer reflector for maximization of optical control, tailoring of beam shape to optimally suit a variety of functions within a space to be illuminated, enhanced glare control and precision light placement as well as energy efficiencies afforded by the ability to use lower wattage lamping than has previously been necessary for suitable work plane illuminance for a given lighting application. The optical systems of the invention utilize two independent and concentrically aligned reflectors working in tandem to smoothly and efficiently produce a versatile range of tailored photometric distributions, the present systems being useful in lighting applications advantageously employing adjustable beams such as accent lighting, ellipsoidal downlighting, stage lighting, landscape lighting, aircraft and automotive reading lighting and even in flashlights as well as in high bay and low bay industrial and retail applications. The optical systems of the invention are now disclosed with particular reference to a high bay luminaire capable of exceptional performance with substantial energy efficiencies.